Question : Which is better G711 alaw, or GSm codecs

I was using on Asterisk 1.6 GSM codec, but I ntoiced that I can not do DTMF inband, so I changed the codec to G711 alaw, and I have noticed a noticeable latency in voice in internal calls (about 5-7 seconds), any advice to avoide this latency?
I am using softphone applications on iPhones.
Both connections are done over the internet.
The dialplan for the internal calls is:
exten => _[2-9]XXX,1,Dial(SIP/${EXTEN},30,tTr)
exten => _[2-9]XXX,n,GotoIf($[${DIALSTATUS}=NOANSWER]?noans)
exten => _[2-9]XXX,n,GotoIf($[${DIALSTATUS}=BUSY]?busy)
;
; Gets to here is call failed for reason other than no-answer or busy
exten => _[2-9]XXX,n,Voicemail(${EXTEN},u)
exten => _[2-9]XXX,n,Hangup
;
; This is for ring-no-answer
exten => _[2-9]XXX,n(noans),Voicemail(${EXTEN},u)
exten => _[2-9]XXX,n,Hangup
;
; This is for busy
exten => _[2-9]XXX,n(busy),Voicemail(${EXTEN},b)
exten => _[2-9]XXX,n,Hangup
   Any help please?

Answer : Which is better G711 alaw, or GSm codecs

Ashraf,

Sorry for the late response. ulaw and alaw work the same way: sample audio at 8KHz and with low frequency plus anti-alias filters you get a frequency response of 300Hz to 3400Hz. alaw audio is sampled with a 13 bit resolution while ulaw use 14 bit resolution. this is why i tend to think it's a better choice. but in the end, they logarithmically compress amplitudes down to 8 bits. And 8 bits at 8KHz equals 64kbit bandwidth: same for both! My mistake about 'wav', this is not a codec but a file format!

* Have you noticed changes in the latency with various codecs ?
* Are you running your PBX in a virtual environment ? If not, what are the specs of your server, and the average CPU utilization ?
* Does the latency occur even with just 1 IP phone connected ?

Thanks.